1. Field of the Invention
The present invention relates generally to electronic circuits, and more specifically to circuits for generating output currents proportional to an input current.
2. Description of the Prior Art
In many types of electronic circuits, it is necessary to provide voltages or currents having fixed ratios with respect to other voltages or currents. For example, many electronic circuits use current mirrors to provide an output current proportional to the input current. Current mirrors and similar current sources are typically used in analog electronic devices for biasing other circuitry into its proper operating range.
In simple current mirrors, the current through an output transistor is driven to be identical to that through an input transistor. In other circuits, the output current is desired to be a fixed ratio, such as two times or three times, that of the input current. An example of the latter circuit is a Wilson mirror, which provides for a current ratio effect as known in the art. Wilson mirrors are known to provide high output impedance, but the precision of the mirrored current ratio is poor.
It would be desirable to provide a transistor circuit having an output current which is an accurate ratio reflecting an input current.